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Writing circuits using nano bubbles

Rendering of bubble-pen lithography where nano spheres are used to write on a surface. Credit: Linhan Lin et al./Nano Letters

At the Cockrell School of Engineering researchers have found a way to write using nano-bubbles with sizes from 1nm to 100nm. These bubbles can be made by particles of gold, silicon and other materials that can be used as an ink to write on a variety of surfaces.

The idea is to create simple circuits, like the ones needed for a sensor, by simply "writing it", a process that can be, with the kind of resolution they have obtained, more precise and most importantly cheaper than etching.

This is not the first time that researchers have managed to print electronics, but so far the printing resulted in more coarse circuits. The possibility of printing at the nanometer scale with high precision brings printed electronic in the same dimension of etched electronics, although at a significantly lower cost.

Clearly, the volumes and the complexity of circuits are greatly different, but for many applications this kind of printed electronics is just enough. It is particularly suited to rapid prototyping of "simple" circuits since printing is so much easier than etching and does not require a clean environment.

The feat is made possible by using a laser that vaporises, with a light burst, a droplet of water creating a bubble that attracts the metal particles desired. The laser beam is controlled by software, like the one used in a 3D printer and using the light beam (at lower power) the bubble is moved to the precise place on the surface where one wants to deposit the metal particles. Once on the surface the laser beams is stopped, the water evaporates and the metal nanoparticles stick to the surface.

By increasing or decreasing the first laser burst one can vaporise more or less water creating bubbles with the desired size.

Researchers are working on further simplifying the apparatus scaling it down to smart phone size so that it can be used in the field. Their dream? Be able to print, on demand, on any surface the sensors one might need at a specific location at a specific time.

Imagine. With your smart phone you download the "specs" of the sensor you need, e.g. to check the presence of a virus in a remote location, and you start printing these sensors on surfaces of homes, schools, public offices. It looks like science fiction, but it is just science.